Bearing and method of making same



R. A. SCHAEFER 3,004,333

BEARING AND METHOD OF MAKING SAME 2 Sheets-Sheet 1 Oct. 17, 1961 Filed June 18, 1957 "-15 1.5. v '.lIll!lllllllllllllllllllllllllllllllll/ FIG.2

9 BY/{/ AK ORNEY INVENTOR. RALPH ASCHAEFER FIG.I

Oct. 17, 1961 R. A. SCHAEFER 3,004,333

BEARING AND METHOD OF MAKING SAME Filed June 18, 1957 2 Sheets-Sheet 2' BEARING LIFE VS BABBITT THICKNESS .032 MAX UNIT LOAD 1330 PSI.

BABBITT THICKNESS IN INCHES o l I l O 50 I00 I50 200 250 300 BEARING LIFE IN HOURS INVENTQR. RALPH A. SCHAEFER ATT RNEY United States. Patent.

3,004,333.. r V I BEARING AND METHOD OF MAKINGSAME Ralph A. Schaefer, Cleveland, Ohio, assignor to .Clevite Corporation, Cleveland, Ohio, a corporation of Ohio Filed June 18, 1957, Ser. No. 666,391

' 6 Claims. (Cl. 29- -191.2)

This invention pertains to bearings, and more particularly to sleeve bearings such as are'used in automobiles, trucks, etc., and to the strip materialfrom which the bearings are formed. 7

Automobile bearings usually consist of a hard metal backing member such as steel to which is adhered a layer of a bearing material such as babbitt, leaded-bronze, copper-lead or the like. These bearings must be able to withstand high loading, high speeds and they must be resistant to fatigue alone and with corrosive conditions. The bearings also must be resistant to suspended dirt carried in the lubricating oil, in the air, and in the fuel systems. Further, bearings must have a low coefiicient of friction, and they should give scoring to the crankshaft. In addition to all of these physical qualities they should be inexpensive. w

Inexpensive babbitt lined strip castbearings are. available but as the automotive trendxtowa-rd'higlier bearing loading continues theyare becoming marginal. Excellent bearings formed of copper-lead with an overlay plate of lead-tin-copper are available to withstand the higher loads but at substantially increasedcostshecause lanthrcasting.

and plating processes are involved in their production.

An object of the present invention is to provide a strip of bearing material, and the method of making same, from which low cost, high quality bearings can be made. It is an object of the present invention to provide an intermediate bearing, that is, one which approaches the cost of the-bimetal type bearing and which has qualities approaching the more expensive trimetal type bearing. 7 Another object of the invention is to -provide a hearing which gives higher duty performance than bimetal babbitt bearings, and which is made by a continuous process.

For a better understanding of the present invention, together with other and further objects thereof, reference is bad to the following description taken .in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

An aspect of the present invention is the provision of a bearing which is made of a layer of strong metal which serves as a backing member, and adhered to one face thereof is a sintered sponge layer of copper-tin bearing material having cavities predominantly on the order of about .001 in size, with the cavities substantially all filled by, a soft bearing material such as babbitt or White metal. g

Another aspect of the invention is the method of producing a strip of bearing material wherein there is spread on the upper face of a steel strip a layer of powdered metal comprising at least in part copper-tin alloy of particle size such that n all particles pass 150 mesh and approximately 50% pass 325 mesh. This layer is gravity sintered at approximately 1900 F. without mechanical compacting to form a sponge layer having about /3 of its volume metal and about cavities which are predominantly on the order of about .0015'2 The temperature of machined ,to a. uniform thickness. The .exposed surface will then consist of low and high melting point constitu- "ice 2 ents. This strip is then blanked and formed into bearings.

'Inthedrawings: 1

FIGURE 1 is an isometric view of a sleeve bearing made in accordance with the present invention."

FIGURE 2 is a block diagram showing the process of the present invention. t f 7 FIGURE 3 is a sectional view through the strip material of FIGURE 2, taken along line 3-3 showing the plated steel strip. 1

FIGURE 4 is a sectional view taken along line 4-4 showing loose powder on the copper plated strip; 7 FIGURE 5 is a sectional view taken along lin'e 5 -5 of FIGURE 2 showing the sintered layer. f f

FIGURE 6 is a sectional view taken along line 6-6 of FIGURE 2, showing the babbitt filled sintered layef.

FIGURE 7 is a graph showing bearing life as a function of babbitt thickness.

FIGURE 8 is a photo-micrograph of a section through a bearing blank made in accordance with the. present invention, with a magnification of diameters.

With reference to the drawings there is shown in FIG- URE 2 apparatus for making the istrip material of this invention. w v

The steel strip 10, from which bearings may be made,

is continuously passed through 'suitablecleaning apparatus and then preferably is copper plated on one of its major faces 11. After plating the strip passes undera hopper 12 which uniformly distributes on-its plated major face a thin layer of special powder, IS. The thin layer of powder is then sintered by passing the strip through a furnace other and which adhere to the steel strip with modest tenacity, By suitable means 16 the strip is brought to 'a temperature of approximately 10 00to 1200 F. which is well above the melting point of the soft bearingmetal constituent. Soft bearing metal such as babbitt 17" is cast onto the strip by means 18 and is immediatelyquenched by means 20. The temperature and time for objectionable reaction between the harder sintered constituent and the softer babbitt is held to a The metallsurface of thesintered layer is readily wetted by the babbitt and the rapid drop in temperature due to quench 2.0 aids in filling the voids. Immediately after casting and while the babbitt on the surface of the sponge is stillliquid the surface is wiped clean of all excess babbitt rightdown to the surface of the sponge, wiper 19being provided for this purpose. Almost simultaneously with the wipingtlie underneath surface of the steel strip is quenchedjby apparatus 20 causing the liquid babbitt to become solid. The process variables and the materials which are used to form the sponge are chosen to produce a'sponge layer which is preferably about .008 to .015" thick, and ,approximately of the volume of this layer is occupied by sintered metal particles while the other /3 prior to castiflg the soft bearing material is made up, of very small cavities. It is of extreme importance that the individual cavities be small since in the finished bearing they are filled withfsoft bearing material the fatigue life of which is rapid-lyreduced asthe thickness of the bearing material increases in any of its planes.

the bearing layer'has been greatly exaggerated.

It is relatively easy to sinter large powder particles onto steel strip and to obtain large cavities which can thereafter easily beifilled with bearing material. However, to obtain uniform cavities which are substantially all on the order of .001 inch and to thereafter fill all cavities with molten material requires close control of materials and process variables. Generally speaking the smaller the cavities the better the fatigue life of the bearing, but it is also true'that the smaller the cavities the harder it is to obtain complete, uniformfilling'with the molten bearing material- In order to achieve close control of the cavity. size in the spongaandin order to prevent the sponge material frombecoming .too hard tobe a good bearing material after tin enrichment during the casting step, it is essential that the initial tin content :of;the powder be kept to a low value in'therrange of from 1 to 2%, the balance being substantially all copper. It hasbeen found when a tincontaining bearing material is'castonto the sponge, even though the casting temperature is kept to a minimum andteven though the steel strip is almost immediately quenched, that there is migration of the tin from the casting material to the copper-tin sponge. Consequently, in order to prevent the copper-tin sponge from becoming too hard tobe a good bearing material, it is essential that the spongeinitially have 12% tin, andthat after enrichment during casting of babbitt or the like that the sponge have not more than about.5% tin.

A sponge of pure copper cannot readily be made on a production line since the melting point of pure copper is quite sharp. To go above this temperature, even slight- .ly, results in low irregular sponge voids and to go below this temperatureresults in incomplete sintering with consequent .poor strength.

Because of the small amount oftin which is used it isimportant that it be added to the copper in the form of a copper-tin alloy. To mix 98-99% copper powder with 2 to 1% tin. powder and then sinter the mixture results-in an unsatisfactory sponge. The proportion .of tin is so small that the resulting sponge is made up of large areas of predominantly pure copper, with poor sponge characteristics, andsmaller areas of hard bronze which will score journal materials.

In order to evenly distribute the 1-2% tin throughout thecopperitis important that at least a significant portion of the powder which is spread on the copper-plated steel strip be pre-alloyed. Thus to form a 99% copper, 1% .tin sponge it .has been found satisfactory to use 90% purecopper powder mixed with copper-tin alloy -powder,'the copper-tin alloy being 90% .copper and 10% tin.

To form a 98% copper, 2% tin sponge it has been found satisfactory to .use 80% pure copper powder mixed with 20% copper-tin alloypowder, the copperetin alloy being 90% copper and 10% tin.

It is, of course, within the scope of the inventionto use other proportions of pure copper powder to copperpowder-may be used, and it follows that 90/ 10 coppertin is not the only alloy which may be used. For example, the alloy may bebetween 85/15 and 95/5 coppertin, and a sulficient quantity be added to the pure copper powder to result in a sponge which has 1 to 2% tin content. The least significant quantity of alloy powder which "will achieve the desired result is that which will result in 1% tin in the sponge, and will give a good uniform sintered sponge without tin rich and tin poor areas.

The additionof at least a significant proportion of copper-tin alloy bronze powder to the pure copper powder results in a broader satisfactory temperature range for sintering and makes a high speed process practical for a production line since high temperatures can be utilized In addition tothe composition, the particle size of the -powder-and the sintering time :and'temperature are .im-

portant in obtaining a uniform, reproducible, fine cavity sponge layer on the steel strip. 7

All of the powder particles of copper must be sufliciently small that they will pass'through a 150 mesh screen, and it is desirable that approximately 50% of the particles pass a 325 mesh screen. ilhe bronze particles must pass a 100 meshscreen. 7

After the power-to be sintered has been uniformly spread to a deptlrof between .012" and .023" on the top surface of the moving steel-strip, the powder is sintered in place without compacting at a temperature between 1830 F. and 1900 F..for a time at that temperature of between /2 and Zminutes. The sintering time andtemperature are correlated. with .the content to obtain uniformly small cavities in the sponge. It has been found that the higher the'tin content, up to about 2l%, and the higher the temperature theless porous the sponge. The powder layer is reduced in thickness by the sintering process, and upon cooling would be found to be between .008" and .015".

Measurementsmade on a sinteredlayerhaving a nominal composition of 2% tin and 98% copper and made in'accordance with the above process show that37-39% of the volume of the layer is cavity and 61-63% is solid. Of the total volume of the layer:

Less than 2% is made up of. voids which are greaterthan 100 microns across.

'3 to.3.5% is made :up of-voidswbich-range between 50 and 100 microns across.

8 to 9% is made up of voids which are .between- 35.and

It is to be noted that the percentage of-the volume of the sintered layerwhich is made up of cavities less than 15 microns is very small, which is highly desirablebecause the extremely small cavities are diflicult to fill with babbitt. It isalso to be'noted that of the volume of the sintered layeronly about 5% is made up of cavities larger than 50 microns. This too is advantageous since large particles of babbitt fatigue more readily than small particles and tear away from the'sponge. Cavities'on the order of .00l'inch (25.4'microns) "to .002 inch occupy 30% of the entire volume of the sponge layer. Thesecavities can be readilyfilled' with babbitt by the process'of this invention and are vsufiiciently small that the fatigue life of a bearing made from this material is excellent.

After the sponge has been sintered onto the surface of the steel strip the composite strip is cooled down to a temperature of 1000 to 1200 F. and it moves under a babbitt casting box where molten babbitt at 700 to 750 vF. is cast onto the sintered surfaces thereof.

The composition of the babbitt is not critical, it being found that to 92% lead, balance tin, is an excellent composition.

It is important, however, to have the strip hotterthan the molten babbitt at the location where the molten babbitt engages the sintered surface of the strip, and his important to quench the underneath side of the strip immediately beyond that location. It is also important to wipe the molten babbitt from the surface of thecomposite strip while it is still in a molten state. Accordingly, immediately after the babbitt casting-box'there is provided a wiper, or squeezer, which wipes olf the excess babbitt right down to the top surface of the sintered sponge layer, thereby facilitating the penetration o'fall of the small cavities by'the molten babbitt.- Simultaneously with the wiping'action'but before the molten'babbitt hardens, the underneath surface of the strip 'is cavities which pulls the molten babbitt into the innermost spaces.

It is very important due tothe extremely small particle size that the molten babbitt be cooled as quickly as possible after it is made to penetrate the extremely small cavities. This is because hard, abrasive alloys are formed when hot babbitt and hot copper-tin sponge are maintained in contact with each other for too long a period of time. These abrasive alloys, if formed, would engage the journal and score it. However, the steel strip must be hotter than the molten babbitt to facilitate filling the extremely small cavities. Accordingly, it is highly advisable that during casting the sintered strip be maintained between 1000 and 1200 F., that the babbitt be about 700 to 750 F., and just as soon as the wiping action is completed that the strip be quickly quenched to reduce to a minimum the formation of the abrasive alloys.

The strip after the sintering and infiltrating steps of the continuous process is then cut to size, the bearing formed, and the bearing surface is then machined to size by the removal of about .005 inch from the bearing surface, resulting in a sleeve bearing whose bearing layer preferably is between .003 inch and .010 inch in thickness, and resulting in a minimum of waste of expensive bearing materials.

FIGURE 8 is a photo-micrograph of a bearing blank, magnified one hundred times, showing the steel strip 10, the self-sustaining sintered sponge layer 15, and softer bearing particlesliljnthe pomesnfjhe sponge 15. Also shown is a layer of babbitt 21 which will be machined off substantially at the line 22 to form the bearing from the bearing blank.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

This application is a continuation in part of application 558,003, filed January 9, 1956, now Patent No. 2,902,748.

I claim:

1. A ship of bearing material comprising a strong metal backing member, a sintered layer comprised of copper-tin bearing metal adhered to one face of said backing member and having cavities predominantly on the order of about .001 to .002 inch in size, and leadbase babbitt bearing metal softer than said sintered layer filling substantially all of said cavities, said sintered layer after filling by said softer bearing metal having a tin content between one percent and five percent, the balance being predominantly copper.

2. A strip of bearing material as set forth in claim 1 further characterized by said sintered layer initially having 1-2% tin and by said softer bearing material containing fin.

3. A bearing formed from the material set forth in claim 1 further characterized by the bearing surface thereof comprising portions of said softer bearing material and exposed portions of said sintered layer.

4. A strip of bearing material as set forth in claim 1, further characterized by said sintered layer being formed at least in part of pre-alloyed bronze powder.

5. A strip of bearing material comprising a strong metal backing member, a sintered sponge layer comprised of a mixture of copper powder and copper-tin bronze powder adhered to one face of said backing member and having cavities predominantly on the order of about .001 to .002 inch in size, said layer being an alloy initially having about 1-2% tin and the balance predominantly copper, and tin containing babbitt filling substantially all of said cavities, said sintered layer after filling by said babbitt having not more than 5% tin.

6. A strip of bearing material as stforth inclaim' 5, further characterized by all of said copper powder passing a 150 mesh screen and by approximately passing a 325 mesh screen, and characterized by said bronze powder passing a mesh screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,164,737 Ford July 4, 1939 2,178,529 Calkins Oct. 31, 1939 2,198,240 Boegehold Apr. 23 1940 2,198,254 Koehring Apr. 23, 1940 2,241,095 Marvin May 6 1941 2,289,658 Koehring July 14, 1942 2,332,733 Lignian Oct. 26, 1943 2,746,134 Drummond May 22, 1956 2,814,095 Lieberman Nov. 26, 1957 

1. A STRIP OF BEARING MATERIAL COMPRISING A STRONG METAL BACKING MEMBER, A SINTERED LAYER COMPRISED OF COPPER-TIN BEARING METAL ADHERED TO ONE FACE OF SAID BACKING MEMBER AND HAVING CAVITIES PREDOMILNANTLY ON THE ORDER OF ABOUT .001 TO .002 INCH IN SIZE, AND LEADBASE BABBITT BEARING METAL SOFTER THAN SAID SINTERED LAYER FILLING SUBSTANTIALLY ALL OF SAILD CAVITIES, SAID SINTERED LAYER AFTER FILLING BY SAID SOFTER BEARING METAL HAVING A TIN CONTENT BETWEEN ONE PERCENT AND FIVE PERCENT, THE BALANCE BEING PREDOMINANTLY COPPER. 